He posted "Went to turn on lights, AC etc… yesterday but I have no power." and I agree this and more is not clear. It's not clear what DC is working and what isn't. It's not clear if the GFCI is or isn't working only that he saw no change.
It's very unlikely that the air conditioner is on a GFCI circuit and if it is it should be a dedicated GFCI CB in the panel and not a plug. " hit test or reset" sounds like a plug and not a CB.
OP Did you measure 12.4V at the battery? Did you measure 124V on the OUTPUT of the CBs? A tripped CB is not always obvious, turn all of them completely off and then on.
Since the problem occured after repairs I would first expect a fuse or CB either AC or DC, next a open or cut wire either AC or DC. Check for AC at the air conditioner and DC for the thermostat circuit for starters.
Mikes last statement is good advice. It can be helpful to give make/mode of the RV and equipment.